Producing petroleum from underground formations



Oct. 7, 1958 R. H. WIDMYER PRODUCING PETROLEUM FROM UNDERGROUND FORMATIONS Filed Aug. 3, 1955 2 Sheets-Sheet l Qi Qu/ l,|ll.| l l l I l llhlllll Oct. 7, 958 R. H. WIDMYER 2,855,047

' RROOUOING PETROLEUM FROM UNDERGROUND FORMATIONS Filed Aug. 5, 1955 2 Sheets-Sheet 2 05 Praz/wing Forma/Yanni@ PRODUCING PETROLEUM FROM UNDER- GROUND FORMATIONS Richard H. Widmyer, Bellaire, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware This invention relates to the production of petroleum hydrocarbons from a subsurface reservoir. More particularly, this invention relates to the production of petroleum hydrocarbons from a subsurface reservoir which is in contact with and overlays a substantially watersaturated formation, or is in contact with and underlies a gas-producing formation, such as a gas cap. Still more particularly, this invention relates to a methodfor controlling coning which sometimes results-during the production of petroleum hydrocarbons from a hydrocarbon-producing formation which overlays a watersaturated, water-producing formation, or which is located adjacent and beneath a gas-producing formation.

Water coning is a term given to the mechanism underlying the entry of bottom waters into producing wells. Petroleum hydrocarbons are often produced from a porous subsurface formation which overlays a watersaturated, Water-producing formation. Under static conditions the water, being of greater density than the hydrocarbons, remains beneath and at the bottom of the hydrocarbon-producing formation. At high rates of production of petroleum hydrocarbons the upper boundary or surface (oil-water interface) of the water-saturated formation rises due to the flow of petroleum hydrocarbons into the well bore which extends into the petroleum-producing formation immediately adjacent and above the water-saturated formation'. The rise of water into the petroleum-producing formation and into the well bore represents a dynamic effect in which the upward directed pressure gradings associated with the flow of the hydrocarbons into the producing well bore balance the hydrostatic head of the resulting elevated water column.

Various methods have been suggested heretofore to eliminate or to reduce the water coning phenomenon. These methods have included reducing the well penetration into the petroleum-producing formation so that rela- Certain underground petroleum-producing formations are only a relatively few feet in thickness. Accordingly, reducing well penetration into such a formation would unduly restrict the recovery of petroleum hydrocarbons therefrom. Other petroleum-producing formations do not have associated therewith an immediately underlying water-impermeable formation or a formation which can conveniently be rendered relatively water-impermeable.

Gas coning is a term given to the mechanism underlying the entry of gaseous hydrocarbons from the gas cap into the underlying normally liquid hydrocarbon-producing formation during the production of normally liquid hydrocarbons therefrom. To a certain extent gas vconing analogous to water coning. Gasiforni hydrocarbons, as present in porous underground formations, are generally States Patent 2,855,047 Patented Oct. 7, 1958 less viscous and more fluent and mobile than liquid hydrocarbons. When liquid petroleum is produced from an underground reservoir which is adjacent and underlies a porous formation containing gasiform hydrocarbons, the gasiform hydrocarbons being less viscous and more fluent than liquid petroleum, move more readily and easily and accordingly penetrate downwardly into the liquid petroleum-producing formation and tend to displace the liquid petroleum during the production of liquid petroleum therefrom. When production of liquid petroleum is commenced near the bottom of an overlaying gas-producing formation, i. e., in the liquid petroleum-producing formation and near the gas-oil interface, it is possible, particularly when a high rate of liquid petroleum is initially employed, that gas from the overlying gas cap eventually will be produced in substantial quantity along with the produced liquid petroleum due to the downward penetration or coning of the gasiform hydrocarbons into the liquid petroleum-producing formation.

Various methods have been proposed to inhibit or prevent gas coning. For example, it has been proposed to render gas impermeable the gas-oil interface between the upper gasiform hydrocarbon-producing formation and the lower liquid hydrocarbon-producing formation by depositing solid material at the interface. This method, however, as well as other proposed methods, cannot be successfully employed in all instances to prevent or inhibit gas coning.

Accordingly, it is an object of this invention to provide au improved method for the recovery of petroleum hydrocarbons from underground reservoirs.

It is another object of this invention to provide an improved method for the recovery of petroleum hydrocarbons from a petroleum hydrocarbon-producing formation which overlays a substantially water-a`turated, waterproducing formation, or which underlies a gas cap.

It is still another object of this invention to provide a method of controlling and/or reducing water coning as evidenced by the production of a relatively large amount of water together with the produced petroleum hydrocarbons during the production of petroleum hydrocarbons from a well bore extending into a petroleurnproducing formation in contact with an underlying waterproducing formation.

Still another object of this invention is to provide a method for controlling and/or reducing gas coning as evidenced by the production of a relatively large amount of gasiform hydrocarbons together with produced liquid petroleum during the production of liquid petroleum from.

a well bore extending into a liquid petroleum-producing formation in contact with an overlying gas-producing formation.

Yet another object of this invention is to provide an improved method of well completion and well production wherein the well bore extends into a liquid petroleumproducing formation which overlays a water-producing formation, or which underlies a gas-producing formation.

ln at least one embodiment of the practice of this invention at least one of the foregoing objects will be achieved.

These and other objects of this invention and how they are accomplished will become apparent with reference to the accompanying drawing wherein:

Fig. l schematically illustrates the water coning phenomenon; and

Fig. 2 schematically illustrates a method in accordance with this invention for controlling water coning, and

Fig. 3 schematically illustrates another embodiment of the practice of this invention as applied to the control of gas coning Referring now to Fig. vl of the drawing which schematically illustrates the Water coning phenomenon, a sub` surface gaseous and/ or liquid petroleum-producing formation is indicated at 11. An immediately underlying substantially water-saturated, Water-producing formation is indicated at 12. A well bore 13 extends into the petroleurn-producing formation 11 and is bottomed in the petroleum-producing formation 11 near the Water-producing formation 12, above the static oil-water interface indicated by dashed line 16. Production casing 14 within well bore 13 is provided with perforations 15 within the petroleum-producing formation 11. Under static conditions (no petroleum production) or at a relatively low rate of production from the petroleum-producing formation 11 the upper surface of the water-producing formation is located at about the position indicated by dashed line. 16, the oil-water interface. However, at relatively high rates of petroleum production, and because of the upward directed pressure gradients associated with the flow of petroleum into perforations 15, the water table or oil-water interface rises to an extent that it is balanced by these upward directed pressure gradients.- As the water table rises, as indicated by solid line 17, into formation 11, the zone of production of petroleum hydrocarbons, water is produced by the lowermost perforations 15 of casing 14, as indicated. Atstill greater rates of production from formation 11 the water table continues to rise and there results a greater production of water relative to the amount of produced petroleum. Eventually at high rates of production, or at high well draw-down pressures, substantially only water will be produced. The above-described phenomenon is commonly known as water coning. v

i Referring now to Fig. 2 of the drawing there is schematically illustrated therein a-method according to this invention for controlling and/or reducing the zone of water-coning. Where applicable, for reasons-of clarity and ease of understanding, the same reference numerals ducing formation in the zone which would be subject to` water-coming.

AsA indicated in Fig. 2 of the drawing, the practice of this invention to control water coning is as follows. Casing.14 is provided with production tubingl 19. Tubing 19 is provided with perforations 20 at the lower end.

thereof yini'petroleum-producing formation 11 and relatively-close to the static oil-water interface 16 and in the zone of the petroleum-producing formation which would be subjected -to water coning if the well was produced byconventional method such as is illustrated in Fig. l. An annular packer Z1 effectively seals and closes the annulus between casing 14 and tubing 19 intermediate the lowermost perforation 15 of casing 14 and the upper- Y most perforations 20 of tubing 19. When production of petroleum is commenced from petroleum-producing formation 11 the resulting produced oil enters perforations 15 of casing 14 and flows upwardlytherein for eventual recovery at the surface. The Water which rises in the resulting water cone is separately produced via perforations 2t) of tubing 19 and is eventually recovered at the surface for disposal or, if desired, for reinjection into the water-producing formation 12 for pressure maintenance purposes.

--By'producing water through tubing 19 a pressure differential A P between P2, the pressure at the location of' water production at about the bottom of tubing 19 in the zone of water coning, and P, the pressure at the static oil-Water interface 16, AP=P-P2, can be maintained substantially greater than the corresponding pressure differential for the same relative positions for the water coning conditions illustrated in Fig. 1 wherein P1 represents the pressure at the zone of production at about the bottom of casing 14. From the above it follows that the pressure differential AP" between P2 and P1, AP"=P2-P1, by producing a well according to the method indicated in Fig. 2, can be made considerably less than the corresponding positions in Fig. l wherein water coning is experienced in the absence of separate production of water from within the water cone. Accordingly if AP" is made small enough insufficient pressure is available to extend the water cone well up to the petroleum-producing interval or to the lowermost perforation 15 of casing 14. AP" can be varied dependent upon P2 which in turn is dependent upon the water production rate from within the water cone.

It is mentioned that it is not necessary to actually liatten the water cone but only to lower the peak of the cone below the oil-producing interval such as is defined by the perforations 15 of casing 14. Thus P1 can be maintained 'for the desired rate of oil production and the water-producing rate via perforations 20 and tubing 19 so that the oil produced via the annulus between casing 14 and tubing 19 is substantially free of water from the water cone can be experimentally determined and in most instances is dependent upon the individual Well conditions and the oil-producing rates desired. As basis for the foregoing it is mentioned that the pressure differential AP, the pressure differential between P and P1, AP=P-P1, for both conditions illustrated in Figs. 1 and 2, is substantially the same, the profile of the oilwater interface (cone) andthe oil-producing interval of each being different, as indicated in Figs. l and 2.

Referring now to Fig. 3 of the drawing which schematically illustrates one embodiment of the practice of this I invention as applied to the control of gas coning, there is schematically illustrated a gas-producing formation or gas-cap 30 which overlies an adiacent oil-producing formation 11, the static oil-gas interface between formations 30 and 11 being indicated by dashed line 31. Where applicable, for reasons of clarity and ease of understanding, the same reference numerals have been employed in Fig. 3 as are employed in Figs. 'l and 2.

. A Well bore 13 penetrates gas-producing formation 30 and petroleum-producing formation 11. Casing 14 is located Within well bore 13, casing 14 being provided with perforations 15 within the petroleum-producing formation 11 relatively close to the static oil-gas interface 31 and in the zone of the petroleum-producing formation 11 which would be subjected `to gas coning if produced by conventional methods. A production tubing 19 is located within casing 14, tubing 19 being provided with perforations 20 at the lower end thereof within the petroleum-producing formation 11. A packer 21 is provided in the" annulus between casing 14 and tubing 19 desirably intermediate the lowermost casing perforation 15 and the uppermost tubing perforation 29, as indicated. Solid line 32 indicates the outline of a gas cone which penetrates downwardly from gas-producing formation 30 into petroleum-producing formation.

In accordance withthe invention as schematically illustrated in Fig. 3, oil and gas are separately produced and gas-coning is simultaneously controlled as follows. Oil is recovered from petroleum-producing formation 11 via perforations 20 and tubing 19. During the productionof oil, gas penetration from gas-producing formation 30 into the petroleum-producing formation 11 in the direction of perforations 20 tends to occur. Gas coning, however, in accordance with this invention, is controlled and inhibited by the separate production of gas from within petroleumproducing formation 11 in the zone thereof most likely to be subjected to gas coning, i. e. within petroleum-producing formation 11 substantially directly beneath oil-gas interface 31 around well bore 13, by separately producing i i i formation.

gas via perforations of casing 14 with the resulting formation of a gas cone as indicated by solid line 32. The gas thus produced via the annulus between casing 14 and tubing` 19 is separately recovered at the surface and desirably is reinjected into the gas-producing formation 30 by means of a gas injection well, not shown, so as to maintain gas pressure Within the gas-producing formation 30. By operating in the above-indicated manner and by suitably adjusting the production rates of the oil from petroleumproducing formation 11 and the gas from Withinl gas cone 32 it is possible to substantially completely prevent gas coning into perforations and to produce oil substantially free of gas originating from a gas cone.

In View of the foregoing disclosure it is apparent that the method of this invention is applicable not only to socalled gas drive petroleum reservoirs, wherein a gas cap overlays a liquid oil-producing formation, but is also applicable to so-called water-drive reservoirs wherein a petroleum-producing formation overlies a substantially water-saturated, water-producing formation.

The practice of this invention `is applicable not only to newly-drilled Wells but is also applicable to Wells which have already been in operation for some length of time and which are producing ka considerable amount of water or gas due to the phenomenon of Water coning or gas coning. ln accordance with a preferred embodiment of this invention, particularly applicable to previously drilled producing wells which exhibit an unduly large amount of Water production or gas production due to water coning or gas coning, respectively, the producing well is shut in for a period of time necessary to approach or establish static equilibrium conditions in the subsurface producing This period of time, depending upon the various circumstances, may be three hours to a month, more or less. After equilibrium conditions have been esta-blished or sufficiently closely approached, as evidenced by the development of a static oil-gas interface, as indicated by dashed line 16 of Fig. 2 or dashed line 31 in Fig. 3, the well is produced in accordance with this invention by separately producing water as hereinbefore described with reference to Fig. 2 or by separately producing gas as hereinbefore separately described with respect to Fig. 3.

. In accordance with lstill another embodiment of the practice of this invention as applied to a liquid oil-producing reservoir which overlays a substantially water-saturated, water-producing formation and which immediately underlies a gas-producing formation and wherein production from the liquid petroleum reservoir tends to give rise .to a water cone and a gas cone, both water coning and -gas coning are controlled in accordance with the practice of this invention by separating producing oil from the liquid petroleum-producing reservoir by-means of an oil production tubing, separately producing gas from the upper portion of the liquid petroleum-producing formation adjacent the gas-producing formation in the zone thereof likely to experience gas coning via perforations in a casing extending into said zone, and separately producing Water from the lower portion of said liquid petroleum-producing formationfin a Zone' relatively close to the water-producing formation and likely to experience water coning via perforations in a water production tubing, which may be advantageously concentrically positioned within the aforesaid oil production tubing. By operating in the aboveindicated manner water coning and gas coning are not only effectively controlled lbut also separate production of water, oil and gas is possible.

Yet another embodiment of the practice of this invention applicable to water coning and/ or gas coning involves substantially continuously producing petroleum from the petroleum-producing formation at a rate which gives rise to coning or the invasion of a coning fluid (water or gas) into the zone of petroleum production and intermittently producing the coning fluid from the petroleum-producing formation in the zone of coning-uid invasion. Still another embodiment, also rapplicable to Water coning and/0r gas coning, involves discontinuing the production of petroleum from the petroleum-producing formation when a substantial or prohibitive amount of coning fluid is produced together with the produced petroleum due to the invasion or" coning fluid into the zone of petroleum production Within the petroleum-producing formation with the building-up of a water cone or gas cone therein and then producing the coning fluid, Water or gas, from the water cone or the gas cone as the case may be.

As will be apparent to those skilled in the art many substitutions, alterations and changes are possible without departing from the spirit or scope of this invention.

I claim:

l. A method of producing petroleum from a petroleumproducing formation which is penetrated by a Well bore, said petroleum-producing formation underlying and in Contact with a gas-producing formation and overlying and in contact with a water-producing formation, which comprises producing petroleum from said petroleum-producing formation via said well bore in a zone surrounding said well bore at a rate which gives rise to a gas cone originating from said gas-producing formation and extending downwardly into said petroleum-producing formation in the direction of said zone and which also gives rise to a water cone originating from said water-producing formation and extending upwardly into said petroleumproducing formation in the direction of said zone wherein said petroleum is produced, separately producing gas from said gas cone within said petroleum-producing formation via said well bore and separately producing Water from said Water cone Within said petroleum-producing formation via said Well bore.

2. A method in accordance with claim l wherein said separately produced gas is returned to said gas-producing formation.

3. A method in accordance with claim 1 wherein said separately produced water is returned to said water-producing formation.

4. A method in accordance with claim l wherein said separately produced gas is returned to said gas-producing formation and wherein said separately produced water is returned to said water-producing formation.

References Cited in the tile of this patent UNITED STATES PATENTS 1,547,194 Arbon `luly 28, 1925 1,644,748 Schweiger Oct. 11, 1927 2,005,767 Zublin lune 25, 1935 2,230,001 McConnell et al. Jan. 28, 1941 2,523,091 Bruce Sept. 19, 1950 

1. A METHOD OF PRODUCING PETROLEUM FROM A PETROLEUMPRODUCING FORMATION WHICH IS PENETRATED BY A WELL BORE, SAID PETROLEUM-PRODUCING FORMATION UNDERLYING AND IN CONTACT WITH A GAS-PRODUCING FORMATION AND OVERLYING AND IN CONTACT WITH A WATER-PRODUCING FORMATION, WHICH COMPRISES PRODUCING PETROLEUM FROM SAID PETROLEUM-PRODUCING FORMATION VIA SAID WELL BORE IN A ZONE SURROUDING SAID WELL BORE AT A RATE WHICH GIVES RISE TO A GAS CONE ORIGINATING FROM SAID GAS-PRODUCING FORMATION AND EXTENDING DOWNDARDLY INTO SAID PETROLEUM-PRODUCING FORMATION IN THE DIRECTION OF SAID ZONE AND WHICH ALSO GIVES RISE TO A WATER CONE ORGINATING FROM SAID WATER-PRODUCING FORMATION AND EXTENDING UPWARDLY INTO SAID PETROLEUMPRODUCING FORMATION IN THE DIRECTION OF SAID ZONE WHEREIN SAID PETROLEUM IS PRODUCED, SEPARATELY PRODUCING GAS FROM SAID GAS CONE WITHIN SAID PETROLEUM-PRODUCING FORMATION VIA SAID WELL BORE AND SEPARATELY PRODUCING WATER FROM SAID WATER CONE WITHIN SAID PETROLEUM-PRODUCING FORMATION VIA SAID WELL BORE. 